Intrarater Reliability of Diaphragm Excursion and Resting Thickness Using Ultrasound Imaging in Subjects With Nonspecific Chronic Low Back Pain.

Objective: The purpose of this study was to establish within-day intrarater reliability values of ultrasound measurements (excursion and resting thickness). Methods: Seventeen volunteers met the inclusion criteria for this preliminary study. The right and left hemidiaphragm excursion and resting thickness were compared between 2 measurement sessions using M-mode and B-mode real-time ultrasound, respectively (30 min apart). Intraclass coefficients, coefficients of variation, standard errors of measurement, and minimal detectable changes were calculated to determine intrarater reliability. Results: The intraclass coefficients of right hemidiaphragm excursion were 0.91 and 0.94 during quiet and deep breathing, respectively. The intraclass coefficient of left hemidiaphragm excursion was 0.95 during quiet breathing. The intraclass coefficients of diaphragm resting thickness were 0.99 and 0.97 in the right and left hemidiaphragm, respectively, which showed high intrarater reliability for ultrasound measurements of both sides of the diaphragm. Conclusion: This preliminary study suggests that diagnostic ultrasonography could be used as a potential method for measuring the resting thickness and excursion of the right and left hemidiaphragm in people with chronic low back pain. Future research with a larger sample size is needed to confirm these findings.